content: /* Copyright (C) 2016-2018 Alibaba Group Holding Limited
  
  Licensed under the Apache License, Version 2.0 (the "License");
  you may not use this file except in compliance with the License.
  You may obtain a copy of the License at
  
      http://www.apache.org/licenses/LICENSE-2.0
  
  Unless required by applicable law or agreed to in writing, software
  distributed under the License is distributed on an "AS IS" BASIS,
  WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
  See the License for the specific language governing permissions and
  limitations under the License.
  ==============================================================================*/
  
  // Protocol Buffers - Google's data interchange format
  // Copyright 2008 Google Inc.  All rights reserved.
  // https://developers.google.com/protocol-buffers/
  //
  // Redistribution and use in source and binary forms, with or without
  // modification, are permitted provided that the following conditions are
  // met:
  //
  //     * Redistributions of source code must retain the above copyright
  // notice, this list of conditions and the following disclaimer.
  //     * Redistributions in binary form must reproduce the above
  // copyright notice, this list of conditions and the following disclaimer
  // in the documentation and/or other materials provided with the
  // distribution.
  //     * Neither the name of Google Inc. nor the names of its
  // contributors may be used to endorse or promote products derived from
  // this software without specific prior written permission.
  //
  // THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
  // "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
  // LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
  // A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
  // OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
  // SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
  // LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
  // DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
  // THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
  // (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
  // OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  
  package com.google.protobuf;
  
  import java.util.Iterator;
  import java.util.Map.Entry;
  
  /**
   * LazyField encapsulates the logic of lazily parsing message fields. It stores
   * the message in a ByteString initially and then parse it on-demand.
   *
   * Most of key methods are implemented in {@link LazyFieldLite} but this class
   * can contain default instance of the message to provide {@code hashCode()},
   * {@code euqals()} and {@code toString()}.
   *
   * @author xiangl@google.com (Xiang Li)
   */
  public class LazyField extends LazyFieldLite {
  
    /**
     * Carry a message's default instance which is used by {@code hashCode()}, {@code euqals()} and
     * {@code toString()}.
     */
    private final MessageLite defaultInstance;
  
    public LazyField(MessageLite defaultInstance,
        ExtensionRegistryLite extensionRegistry, ByteString bytes) {
      super(extensionRegistry, bytes);
  
      this.defaultInstance = defaultInstance;
    }
  
    @Override
    public boolean containsDefaultInstance() {
      return super.containsDefaultInstance() || value == defaultInstance;
    }
  
    public MessageLite getValue() {
      return getValue(defaultInstance);
    }
  
    @Override
    public int hashCode() {
      return getValue().hashCode();
    }
  
    @Override
    public boolean equals(Object obj) {
      return getValue().equals(obj);
    }
  
    @Override
    public String toString() {
      return getValue().toString();
    }
  
    // ====================================================
  
    /**
     * LazyEntry and LazyIterator are used to encapsulate the LazyField, when
     * users iterate all fields from FieldSet.
     */
    static class LazyEntry<K> implements Entry<K, Object> {
      private Entry<K, LazyField> entry;
  
      private LazyEntry(Entry<K, LazyField> entry) {
        this.entry = entry;
      }
  
      @Override
      public K getKey() {
        return entry.getKey();
      }
  
      @Override
      public Object getValue() {
        LazyField field = entry.getValue();
        if (field == null) {
          return null;
        }
        return field.getValue();
      }
  
      public LazyField getField() {
        return entry.getValue();
      }
  
      @Override
      public Object setValue(Object value) {
        if (!(value instanceof MessageLite)) {
          throw new IllegalArgumentException(
              "LazyField now only used for MessageSet, "
              + "and the value of MessageSet must be an instance of MessageLite");
        }
        return entry.getValue().setValue((MessageLite) value);
      }
    }
  
    static class LazyIterator<K> implements Iterator<Entry<K, Object>> {
      private Iterator<Entry<K, Object>> iterator;
  
      public LazyIterator(Iterator<Entry<K, Object>> iterator) {
        this.iterator = iterator;
      }
  
      @Override
      public boolean hasNext() {
        return iterator.hasNext();
      }
  
      @Override
      @SuppressWarnings("unchecked")
      public Entry<K, Object> next() {
        Entry<K, ?> entry = iterator.next();
        if (entry.getValue() instanceof LazyField) {
          return new LazyEntry<K>((Entry<K, LazyField>) entry);
        }
        return (Entry<K, Object>) entry;
      }
  
      @Override
      public void remove() {
        iterator.remove();
      }
    }
  }
  